Rheostat



A. F. C. LOTZ RHEOSTAT Aug.l23,1927. Y 1,639,951

Filed Maron ze. 192:5l

I 'Lung lll Patented Aug.v 23, 192?.

NITEn srA OFFIC..

ALEEEI) E. C, LoTz, or CHICAGO, ILLINOIS, AssIeNoE To ELECTRICAL ENGINEERS EQUIPMENT COMPANY, or CHICAGO, ILLINoIs, A CORPORATION or ILLINOIS.

REFJQSTAT.

Application led March 26, 1925: Serial No. 13,523'.

My invention relates to rheostats or resistance devices which are of particular utility in the radio lield. Among the im. portant objects of the invention are: to provide construction and arrangement which will permit easy and accurate relative movement between' a contact member and a resistance element, but which will insure suflicient area of engagement of the resistance member to prevent sparking or heating; to provide for a substantially frictionless rolling engagement between the contact element and the resistance element to thus prevent Wear of the elements, particularly the resistance element, so that theresistance value of said .resistance element'will remain constant; to provide construction and arrangement In which the contact and resistance elements are securely held together at all times in firm electrical engagement, yet Will be easily.

operable; -to provide construction and arrangement Which will permit very accurate and reliable resistance adjustment to be made; and, in general, to produce a device which is simple in construction and arrange? ment, free f rom Wear, .and with which ne and dependable resistance adjustment can readily be made. l

. 0n the accompanying drawings,

Fig. 1 is a rear elevational View of the rheostat device with the closure cover removed;

Fig. 2 is a sectional View on` line 2+,2 of Fig. l;

Fig. 3 is a sectional View on line 3-3 of. Fig. 1; and

I Fig. 4 is a perspective view of the contact roller supporting spring frame.'

A cyli drical cup or container 10 of insulating material, such as bakelite, houses the resist-ance controlling element and has a detachable @over 11 locked'in place by bolt 12. Seatingagainst the innerl side of the cylindrical Wall of the container -isnthe resist-ance element 13, which is preferably in the form of a band or strip of 'suitable resistance metal or resistance composition. The ends of the 'resistance member are' connected with terminal structures 14 and 15 mounted on the container wall, which terminal members may be the sole means for holding the resistance member in place, or addi, tional securing means may be used. As shown, the ends of the resistance member shaft.

`wall forms a backing therefor.

Extending axially from the base Wall of the container 10 is an externally threaded sleeve 16 which is shown secured to the container by threading engagement and by means of the lock nut 17. The sleeve 1 6 journals the shaft 18, which, at its outer end, has the knob 19 by means of Which the shaft may be t-urned to operate the movable conta'ct mechanism within the container. l/Vithin the container is a contact roller 2O connected with the shaft 18 by means of a spring frame F. This spring frame is formed from av single piece of sheet metal. It comprises a body part 21 from Whose sides extend the parallel arms 22, 23 for receiving between them the contact roller 20, the shaft `br axle 24 of this roller journaling in the holes 25 and 26 in the arms. The body is bent to form spring loops 27 land 28 and spring ends 29 .and 30 parallelwith the body 21, and from the diagonally opposite corners'of the spring ends 29 and 30 extend the arms 3l and 32 which are parallel. with each otherpand with the arms 22 and The arms 31and 32 have openings 33 receiving the reduced inner end 18 of the shaft 13, the frame being rigidly secured to the shaftend torotatewith the shaft. As

shown, the shaft is flat on one side andthe openings 33 arecorrespondingly Hat, so that the frame will be non-rotatably` held on the The. frame is electrically connected with the terminal structure 34 on the container 10, the connection being by` means of an L-shaped bar 35 having one end secured tol the terminal 34 and the other end perforated to receive the shaft end 18 between the frame F and the shaft shoulder 36. The outer` end of the shaft end 18 is threaded for receiving the nut 37, a spacer sleeve 38 being applied to the shaft end between the arms '31 and 32 of the frame, so that when the nut 37 is applied, the frame, the sleeve, and the bar 36 Will be securely and electrically clamped to theshaft.

The contact roller 20 is of-good electrical conductive material and is lforced by -the spring` frame F toward the resistance element, but instead of having the yroller en- Ico gaged directly with the element, lI interpose f tact roller against the ring 39 and the ring ties.

39 against the resistance element,l the roller rolling along the inner face of the ring and the ring onits outer face rolling along th resistance element. Such rolling engagement practically /eliminates friction, and consequently the roller and the ring, and

`particularlyfthe resistance element will not e worn away and the resistance element will therefore maintain its full resistance capacity and will not change, as is`thelcase in devices where the frictional engagement will eventually wear down the resistance element and materially change its resistance proper- This Jfrictionless rolling engagement and travel of the parts will permit the more accurate and easy rotation of the adjustment controlling knob 19. r

The spring walls 29 and 30, together with the spring loops 27 and 28, will maintain uniform and suiiicient pressure against the contact roller to insure the proper pressure of the Contact ring with the resistance element or material for the most eiici'ent results. The cylindrical wall of the container 10 forms a rigid backing for the resistance material under suchcontact member pressure. The ring 39 surrounds thel body4 of the spring F and engages between the arms 31 and 32 thereof. To assist the arms in holding the ring inproper alignment with the resistance material, the contact roller hasthe side flanges 40.

The entire resistance device can be read-- ily supported from a panel 41 by means of clamping nuts 42 and 43`engaging` the sleeve 16. By means of the three terminals, the device may be used for ordinary resistan`ce yadjustment orl as a potentiometer, and

`on account of the construction andarrangement described, very fine adjustment and regulation can be made and accurate and reliable results obtained. As changes and modifications can be made which will so,

come ,withinthe scope of the invention, I do not desire to be limited to the precise construction and arrangement shown.

I claim' the following v 1l. In a resistance adjusting device, the combination of a circular resistance `e'lement, Va circular contact member therefor of less diameter, a frame withinsaid contact member journaled in the axis of said refsistance element, a vroller on said frame, said frame being of spring material and pressing said roller radially outwardly to cause said contact member to be held against said resistanee element, said roller having rolling engagement with said contact member, and said contact member having rolling engagement with said resistance element when said frame is revolved7 and circuit terminals connected with said Contact member and said resistance element.

2. Ina resistance adjusting device, the combination of a cylindrical container, a resistance element supported against the inner face of said container concentric therewith, a shaft extending axially in said container, a frame fixed at one end to said shaft, a roller at the other end of said frame, said frame intermediate its ends being formed to produce spring pressure against said roller, and an annular contact member interposed between said roller and resistance element, said roller having rolling engagement with said contact member and said contact member having rolling engagement with said resistance element when said frame is revolved, and termina-ls on said frame connected with said contact member and resistance'element,

y 3. In a resistance adjusting device, the combination of a container having a cylindrical wall, resistance material sup rted on the inner side of said, wall, a sha' extending axially in s'aid container, a sheet metal frame lsecured at one end to said shaft, a roller journaled on the outer end of said frame, an .annular contact member interposed between `said roller and resistance material, said frame intermediate its end beingbent to. form a spring and exerting outward pressl'ire against said roller, whereby said contact member will be clamped between said roller and resistance material, said roller havin rolling engagement with said contactmem er, andsaid contact member having rolling engagement with said resistance Inaterial when said frame is revolved.

4. In a resistance adjusting device, the combination of a container having a cylindricalwall, resistance material supported on the inner side of said wall,` a frame, an axial shaftv supportin roller journale at the other end of said frame, a circular contact member interposed betweenfsaid roller and resistance material, spring means on said frame acting a ainst said roller whereby said contact inem r is pressed against said resistance material, means on said roller for confining said c'outact member axially, and terminals connected' with said Contact member and resistance element, said roller having ro'llin engagement with said contact member an .said contact member having rolling engagement with saidk frame at one end, a-

said resistance material when said frame is revolved.

5. In a resistance device, a casing, a resistance member within Said casing, a contact member urged toward the resistance member, said members being disposed in a common plane and having relative movement in said plane lengthwise of the resistance member, a second contact member confined between the first contact member and the resistance member, said first contact member traveiling on the second contact member and pressing it against'the resistance member, and means coacting with the two contact members for maintaining the second contact member in the plane of the first contact member and the resistance member and out of contact with the casing.

6. In a resistance device, a stationary resistance member, a contact member urged toward the resistance member and movable lengthwise thereof. a second contactmember confined between the first contact member and the resistance member, the first contact member traveling on the second member and holding it in contact with the resistance member, and means carried by the first contact member confining the second .contact member laterally and 'maintaining it in the Vplane of said first member and the resistance member.

7. In a resistance device, a stationary resistance member, a contact member urged toward the resistance member and movable lengthwise thereof, and a second Contact member confined between the first contact member and the resistance member, said first contact member having lateral flanges confining the second contact member laterally and maintaining it in the plane of the first contact member and said resistance member, the first Contact member travelling on the second contact member.

8. In a resistance device, an annular resistance member, a frame movable about an axis concentric with the resistance member, a roller carried by the frame and urged toward the resistance member, said roller having lateral peripheral flanges, and an annular contact ring disposed about the roller and confined between the flanges, said ring being held by the roller in contact with the resistance mem-ber.

In witness whereof, I hereunto subscribe my name this 23rd day of March, 1925.

ALFRED F. C. LOTZ. 

